In recent years, flat panel display devices that use flat panel display elements such as liquid crystal panels and plasma display panels are replacing cathode ray tube displays in display elements for image display devices such as television receivers, allowing image display devices to be made thinner. Liquid crystal panels used in liquid crystal display devices do not emit light on their own; therefore, it is necessary to provide a separate backlight device as an illumination device. As an example of such backlight devices, a direct-lit backlight device that directly supplies light to the liquid crystal panel from the rear surface side thereof is known.
Among direct-lit backlight devices, a configuration is known in which a reflective sheet for reflecting light emitted from a light source and traveling in a direction opposite to the display surface back towards the display surface is laid on a light source substrate and on the bottom plate of a chassis, which is a case. In a backlight device configured in this manner, in some cases, the reflective sheet warps in the vicinity of the light sources due to heat generated thereby, resulting in portions of the reflective sheet in the vicinity of the light sources to rise up. If the portions of the reflective sheet near the light sources rise up, then some of the light emitted from the light sources and traveling towards the display surface is blocked by the raised reflective sheet, resulting in uneven brightness in the display surface. An example of a direct-lit backlight device that can mitigate uneven brightness in the display surface resulting from the reflective sheet rising in this manner is disclosed in Patent Document 1, for example.